Microgravity Experiments on Ferrofluids

Magneto viscous effects as well as thermal transportation phenomena in magnetic fluids have been a topic in microgravity research for some time already. In order to prove tension differences in ferrofluids, use is for example made of the rising of a free surface on a rotating shaft, the so-called Weissenberg-effect. The rising of the liquid is dependent on 1/g, so that under microgravity also weak tension forces in ferrofluids can be detected easily (Volker 2002). In the frame of an ESA Map project66 an experimental set-up is developed at present for the investigation of thermal transportation phenomena in ferrofluids (e.g. the Soret effect). The hardware for the employment in the European Drawer Rack on ISS is developed in co-operation of Astrium and the Center for Applied Space Technology and Microgravity in Bremen (ZARM). NASA is already conducting microgravity experiments on ferrofluids on the ISS in the frame of the project in-SPACE ("Investigating the Structure of Paramagnetic Aggregates from Colloidal Emulsion"). Here the phenomenon is examined, that magnetic particles in ferrofluids clump together by the influence of high frequency exterior alternating magnetic fields, whereby the magnetorheological characteristics of the ferrofluids get lost. This effect does not occur in mixed ferrofluids, but can be problematic however for certain applications. The clumping process, which extends over a period of up to several hours, is affected strongly by gravity, so that exact patterns of the particle complexes can be studied only under microgravi-ty.67 Due to the long-lasting processes and the availability of human astronauts the ISS is the suitable platform for this experiment.

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